In article 27926@ncsu.edu, Shane Trent <sdtrent@mte.ncsu.edu> () writes:
>Hello,
>
>I read years ago that the optimum length of an antenna is 1/2 wavelength
>of the frequency being received, this article was talking about
>commercial FM. Is this true (no equations needed)?
>
>Also, would this apply to a dish antenna? What size microwave (900 MHz)
>should be used?
>
>Thanks for your help,
>-shane
Shane,
An antenna's length (physical- electrical) determines what frequencie(s) it will resonate at, or
in other words, receive/transmit optimally. Most antenna systems - refer back to a 1/4 wavelength. It is
common to use a 1/2 wave dipole arrangment - this also provides some gain over a 1/4 wave antenna. You
might want to get or look at the radio amateur handbook - this area is quite diverse, in any case, for an
antenna to work well it must resonate at the desired frequency and be matched(impedance wise) to the transmission line that feeds/connects to it. In the case of a microwave dish - you are fooled by its appearance. The actual antenna is located in the center of the dish at the focal length of the parabola. The so called dish, has a paraboloic curvature - this provides for its usefullness. I won't get into the reasons why - it would take too much here and now. The diameter of the dish provides the "gain". The antenna itself is usually a 1/2 Wave dipole - or 1/4 wave stub.
